The present invention relates in general to inclination and acceleration sensors, and in particular to a sensor operating based on capacitive detection of a position of a ball.
Conventional position sensors rely upon the detection of electrical (ohmic) contact between a movable element and a stationary sensor. Such systems typically employ either an electrically conductive ball or a liquid-like material such as mercury as the movable element. There are disadvantages associated with such systems. Reliance on a conductive (e.g., metal) ball for example makes the system susceptible to dust, oxidation, and erosion. Mercury-wetted systems on the other hand require special housing, are toxic and tend to be more expensive.
There have been inclination sensors developed that operate based on detecting capacitive variations. Such systems typically employ some type of liquid that is placed inside a domed or spherically-shaped housing. The walls of the spherically-shaped housing act as capacitive plates such that any movement of the liquid affects a change in the measured capacitive value. Examples of these types of sensors can be found in U.S. Pat. Nos. 4,422,243, 4,624,140, 4,707,927, and 5,079,847. Other types of inclination and acceleration sensors have been developed employing magnetic or inductive elements and semiconductor or silicon based components. Each one of these systems is developed for a particular application requiring a specific degree of precision and speed of detection. Most, however, are not suitable for a low cost, compact design that can be incorporated onto for example a small printed circuit board.
There is therefore a need for a reliable and cost-effective inclination and acceleration sensor.